Dictionary of Ichthyology  

protrusible = capable of being protruded, extended or thrust out, e.g. the upper jaw or both jaws project forward to form a tube or scoop-like cutting surface.

Hyperoplus lanceolatus above and Ammodytes hexapterus below, from A. P. Andriashev's "Fishes of the Northern Seas of the U.S.S.R.", 1954.

Canadian Museum of Nature